Engine Longevity

[FF]

With the current engine assembly systems the engine should be the same , its the operators choice to operate at M1 or M4 , not the engine build.

Using the 24/7 engine rating would be a good choice for most long range cruisers , as there should be plenty left for the occasional use to make a big wake..

 

[kapnd]

Delfin wrote;
“My question is, how many actual physical differences are there between engines of the same manufacture and model, but different ratings, or are they primarily how the engine is governed? If the latter, then isn't rating somewhat unimportant in a full displacement vessel since whatever the rating, the engine will likely be run at less than 40% load?”

I see the perfectly powered (loaded) engine in a FD rec trawler as about 60 or so percent. Mine is 50% and I know I could do easily w less power. But it depends on who or what rates the engine. My Mitsubishi is a generic industrial engine. And Westerbeke and Vetus both claim more power .. 44 and 42hp.

The differences are not physical, they are in the terms of the warranty.
If you run your motor beyond spec and blow it up, the warranty is voided.
The manufacturers always cover their asses!

 

[Nomad Willy]

I think the overwhelming thing that wears out engines is the pressure exerted on the piston and cyl wall by the offset crankpin and connecting rod. The forces downward on the piston crown are the result of an explosion. Much of that force, because of the offset conecting rod, is exerted to the piston. The force pushes the pistion against the cylinder wall where there is only a small amount of oil to keep pistons from abrading cylinder walls or more likely cylinder walls from abrading pistons. I don’t see how they survive at all. The only other place dealing with such forces is the cam lobes and their followers.

Slow warm ups, good oil and light loading is about all one can do to reduce the wear. But reducing engine speed wouldn’t reduce the heavy forces much. Only reducing throttle or load can help significantly. Perhaps an underloaded engine turning more (relatively) rpm is the best road to long lasting engines. So essentially more noise = the longest lasting engine.

Art mentioned several times an additive that was very good at high wear points .... Art?

 

[Insequent]

With the current engine assembly systems the engine should be the same , its the operators choice to operate at M1 or M4 , not the engine build.

Using the 24/7 engine rating would be a good choice for most long range cruisers , as there should be plenty left for the occasional use to make a big wake..

for JD at least, the different ratings can be programmed/set in the ECU by the dealer. Its fuel mapping for the injector pump, and often lower max. rpm setting as well. The result is a different max. HP & torque, and slightly different shaped curves as well.

The attached pdf's illustrates this. I have the 6068TFM75 in M3 setting, for 201HP. The M1 & M2 have lower max rpm, and 158 & 178 HP respectively. I just noticed the M1 effectively reaches max power, and max torque, at 1800rpm so it seems to be set-up to run a genset.

I normally run at 1600rpm, with a 30-35% load factor. I could run 400rpm below max, or 2200 rpm, continuously if I wanted to, but have no need to do so.

 

[DDW]

Not a mainstream trawler engine but perhaps relevant: I have a Volvo diesel in the sailboat, the block says Perkins on it but is actually a Shibaura/IHI engine. It is sold in two versions, normal and turbocharged aspiration. I have the turbocharged version. The turbocharger developed problems, I investigated the possibility of removing it, thinking that maybe the injection pump, governor, and injectors might have to be changed. But I would have the benefit of the stronger pistons and whatever else went into the turbo engine (75 hp vs. 55). The distributor and myself did a detailed comparison of part numbers of every part in the engine. They were identical except for the turbocharger and exhaust elbow. The only difference was the adjustment on the governor stop screw, allowing the fuel rack to travel further in the 75 hp. Governor rate (springs, weights) were the same.

On a common rail engine it is even easier, just reflash the ECU with different code. That is what Ford and Chevy do with their pickups - the derated engine in the chassis cab just has different code in the ECU.

 

[kapnd]

Nomad Willy, re post 123
I’ve always relied on my ear to set the throttles. I think increased noise level is a certain indication of elevated stresses in the motor, so my theory is to pull em back till the noise relaxes.
I’ve seen very few bottom end failures on diesels, especially the slower revving ones like Cat, Cummins, JD, but Volvo’s and Yanmars come in with holes in the cases, bones showing! Speed kills!

 

[Searios]

I have a CPP. I'm operating it at max torque RPM, where the engine performance chart says that max fuel burn is 19 liters/hour. The max fuel burn is 32 liters/hour @ max RPM.

My actual fuel burn is around 11 liters / hour.

So, theoretically and according to the different load theories, my engine is loaded either 57% (11/19) or 34% (11/32).

I always run the propeller at full forward pitch, which gives an EGT of around 400-450F which is well below the max operating temp.

But after reading this thread, the articles and the comments about variable pitch propellers I'm now doubting weather my engine load is closer to 100% as some comments seems to imply..

 

[sunchaser]

Not a mainstream trawler engine but perhaps relevant: I have a Volvo diesel in the sailboat, the block says Perkins on it but is actually a Shibaura/IHI engine. .

Perkins/Shibaura is a JV with several different factories. This JV is one of several that Perkins has entered into around the world during the past few decades. Staggering as to the the number of Perkins JV engines produced every year.

Just curious, salt water in the turbo? Sail boat exhaust issues can get interesting due to heeling and depth below WL.

 

[DDW]

What happened was at some point it was noted that the engine was making more smoke. I'm not entirely sure when it began, it was after a somewhat lengthy layup. Not sure how long it ran that way. When I investigated, the turbo wheel did not move, it was touching the hot housing. Volvo wanted $3k for a replacement, which led me to investigate how I might live without it.

IHI makes the engine and the turbo. The engine is quite common in New Holland loader and plows, Bobcats, etc. A new replacement turbo for those can be had for around $300 - 400. The difference between all the variants is just the turbo wheel trim. But no way I could ID the turbo wheel, IHI and Volvo are sworn to silence I guess. I took it to a rebuilder who says he sees quite a lot of this: either salt water or salt air eventually corrodes the housing which grows enough to interfere with the wheel. It cost me about $600 to clean it all up and ceramic coat the housing (which he said reduces the likelihood of a repeat). For that money, I put it back on - I was going to have to get a different exhaust elbow and a couple of other parts, remove the intercooler, etc, if I changed it over. It's been running well since.

The engine is pretty low, not that much drop from the turbo/elbow into the muffler. I doubt water ever backed up in there, but you have to figure it is saturated with salt air always. I never noticed any drop in power, but then I run it conservatively, 2000 rpm cruise, load is probably 30-40%. That's why I figured I could live without the turbo if I needed to.

 

[Simi 60]

Have wondered the same (removing turbo) on our NTA855 reverting back to N855
Rarely runs above 1250rpm, 99% of the time we're at 1150 so turbo not working.
Occasional run up to 1500 to blow the cobwebs out but never see any smoke, just noise and increased fuel burn

 

[FF]

"But after reading this thread, the articles and the comments about variable pitch propellers I'm now doubting weather my engine load is closer to 100% as some comments seems to imply.."

I would start out with modest pitch and observe the EGT gauge as you increase pitch.

THe EGT will go up as the prop loads increases , and then drop off IF the pitch is too large as the prop will cavitate.

Usually this rumble can be heard and felt below near the prop.